Thermal copying process



June 2, 1964 E. P. DAMM, JR., ETAL 3,135,621

THERMAL COPYING PROCESS Filed Aug. 11, 1961 FIG.1

INK

NON-ABSORBING COPY- R 35-ORIGINAL.

PATTERN 23-suRFAcE 4| --LENS SMOOTHING DOCTOR BLADE BLADE FOR RECOVERY AND SALVAGE OF THE DRIED INK INK RESERVOIR HEAT RAYS F I 2 47-S0URCE OF 5lOR|GlNAL PATTERN 'INVENTORS SEE E SZ J.A.UNDERH|LL 49 E.P.DAMM,JR.

United States Patent The present invention relates to a thermal copying process for transferring to copies imagewise and indiciawise liquid ink which defines a replica of a pattern to be copied. More particularly, liquid ink applied to a printing member is dried to a non-tacky residue by radiant heat except in remaining areas defined by a pattern which blocks the radiant heat. The liquid ink in these remaining areas is then transferred to copy material imagewise and indiciawise.

According to the invention an original document to be copied is placed in a path between a source of heat rays and a printing member.

Ink is applied to the printing member; this ink is nor mally liquid at room temperature and dries to a nontransferable state at higher temperatures resulting from the patternwise application of radiant heat.

The original document has a pattern defined by areas thereon which are relatively absorptive of the heat rays and other areas thereon which are relatively non-absorptive of the heat rays. Only those heat rays not absorbed by the original document reach the printing member, thereby drying the ink to a non-transferable state only in areas eorresponding'to the non-absorptive areas of the original document. The ink on the printing member remains liquid and transferable only in those areas corresponding to pattern-defining absorptive areas on the original document. The transferable ink is then transferred to copy material to provide an imagewise and indiciawise replica of the pattern.

It is known from the prior art that thermal images may be used for modifying a thermally sensitive medium to selectively print therefrom; for example, the Sperry-Rand patent for demagnetizing portions of a uniformly magnetized surface by means of a thermal image. It is also known from the patent to J. C. McCarthy, No. 1,862,189, isued on June 7, 1932, to use a non-drying masking material disposed in a design on a surface which is coated, the masking material and the coating thereover being later removed by washing the masking material with its solvent. Other prior art teaches the removal of materials in order to establish a pattern or film, but there is no patent of which we are aware that teaches the selective drying of a liquid for printing.

In one form of the invention an ink normally liquid at room temperature but which dries at a higher temperature is applied to form a film on a printing member which does not absorb the ink. An original document having a pattern to be copied is placed adjacent the surface of the printing member. A source of radiant heat is located at an exposure station so that rays therefrom pass through the original document against the printing member. The pattern itself, which may be markings on a sheet of paper, for example, blocks certain of the heat rays. The ink is dried to form a film residue on those areas of the printing member exposed to the heat rays. The ink in the remaining areas blocked from the heat rays by the pattern remains liquid and is transferred to copy material by print ing to provide an imagewise and indiciawise replica of the pattern.

In an alternative form of the invention, heat rays are reflected by the original pattern through a lens to a printing member, the markings on the liquid reflecting an in- Too suflicient quantity of heat rays to dry the ink, so that a liquid ink image corresponding to the markings on the original remains on the printing member.

For convenience, the word ink shall be used herein, it being understood that the word coating also could be used to describe the pigment-containing liquid composition used in the invention;

In carrying out the invention, the liquid ink composition must be continuous and must be liquid at room temperature. The liquid ink must be capable of being dried by evaporating the liquid vehicle of the ink to provide a non-transferable, continuous non-tacky film residue. The evaporation to the dry, non-tacky film residue is preferably completed by application of heat in a matter of A to 10 seconds and is effected by radiant heat or by a relatively quiescent atmosphere which does not mechanically displace the ink.

The liquid ink must contain at least the following essential ingredients:

(1) A volatile vehicle which is normally liquid at room temperature and which assumes the vapor state at elevated temperatures, e.g., above C. and up to 225 C. and

(2) A solid marking pigment suspended in the liquid vehicle which serves to represent indicia or design in the residue after transfer of said liquid film to the stock being painted and after evaportion of the liquid vehicle from said transferred film.

An example of a liquid ink used in carrying out the invention is an ink consisting of particles of colloidal graphite as a binder suspended in a solution of isopropanol. Other liquid inks are known which will provide the desired characteristics, but the particular composition of the liquid ink used is not a part of this invention.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawmgs.

For a better understanding of the invention, reference is made to FIG. 1 which is a schematic diagram of an embodiment of the invention and FIG. 2 which is a schematic diagram of an alternative form of the invention. In FIG. 1 there is shown a printing member 21 which may be a flat plate but which is shown preferably as a roll has a printing surface 23 which is of material that does not absorb ink. This material on surface 23 may be rubber, metal or any material having a glossy, non-absorbing surface so that dry ink residue may be easily removed therefrom. The surface 23 is passed through a reservoir 25 containing liquid ink of the type previously described, so that a thin film of ink covers printing surface 23. A doctor blade 27 is suitably located to brush away the excess dried ink on printing surface 23. The excess ink is recovered in a conventional manner.

As shown in FIG. 1, a conventional smoothing blade v31 is provided to smooth the film of ink after removal from the reservoir 25. A source of radiation producing infrared rays or other heat-producing electromagnetic radiation is located at 33. Betwen the source of radiation 33 and the roller surface 23 is placed an original pattern 35 of material which is transparent to infrared or other heat producing rays and which is to be copied. Rollers 37 and 39 are shown for convenient handling of the pattern, especially if it is paper having markings thereon.

Located between the pattern 35 and surface 23 and on a line with the source 33 is a lens 41 which focuses or images the heat rays reaching the surface 23.

A material 43 such as paper but which may be any suitable material on which the copy is to be made is fed into the system and is conveniently placed in contact with 7 heat rays from source 33 to corresponding areas of the printing surface 23, the ink in those corresponding areas remains liquid. Thus, in correspondence to the lack of heat rays reacting surface 23 the liquid ink remaining on surface'23 defines a replica of the pattern 35, and this liquid ink is transferable to copy 43 to provide imagewise and indiciawise printing of the replica on the copy 43. The ink film on residual areas of the surface 23 dried by able and thereafter transferi-ing said liquid inkto said copy sheet.

2. A method of printing from an original pattern a" transferable image of ink for positive copies on to a copy sheet comprising the steps of applying to a roll transferable ink containing a solid marking pigmentwhioh is nonvolatile and non-tacky which becomes non-volatile liquid transferable when subjectedto drying by heat; said ink consisting of particles of a non-melting colloidal pigment, such as graphite, suspended in a volatile solvent; radiating heat producing rays to said roll thereby driving off the volatile. liquid part of said transferable inkto leave a the radiant heat to a non-tacky (i.e., hard) state is nontransferable to the copy.

It will be appreciated that any pattern having portions which block the heat rays from source 33 will provide a replica of liquid inkon the printing surface 23.

An alternate form of the invention is the reflection projection system shown in FIG. 2 for providing copies of original documents which are not sufficiently transparent to heat radiation for the passing of heat rays therethrough. An example of such an original is markings on paper. As shown in FIG. 2, heat sources are provided at 4'7 and 49 to emit heat rays which impinge against the surface of an original pattern 51 011 which, for purposes of illustration only, a printed letter A is shown as a darkened marking thereon. The heat rays emitted from sources 47 and 49 are reflected by the original pattern 51 through a focusing lens shown at 53 between theoriginal pattern 51 and a roll 55 containing liquid ink according to the invention. Because the reflectivity of the unmarked portion of the original pattern 51 is significantly higher than that of the darker marked portion illustrated as an A thereon, the reflected heat rays from the unmarked portion of original pattern 51 are reflected through lens '53 to roll 55,- drying the ink thereon to a non-transferable state. However, the marked portion at A does not reflect a sufficient quantity of radiation from sources 47 a and 49 to dry the ink in a corresponding area onroll 55,

said ink in the corresponding area therefore remaining liquid and transferable imagewise and indiciawise to a copy in the same manner as described in conjunction with FIG. 1.

While the invention has been particularly shown and described with reference'to preferred embodiments there- I of, it will be understood by those "skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A method of printing from an original pattern to a copysheet a transferable replica of liquid ink comprising the steps of applying to a printing member a volatile liquid transferable ink containing a solid marking pigment which is non-volatile and non-tacky which dries to form a continuous non-tacky film and becomes non-transferable whendried by heat; said ink consisting of particles of a non-melting colloidal pigment, such as graphite, suspended in a volatile solvent; radiating heat-producing rays to said printing member thereby driving off the volatile liquid part of said transferable ink to leave a nontacky, non-transferring film; and blocking some of the rays by a pattern so that the ink in areas of the printing member corresponding to the blocked rays remains transfernon-tacky, non-transferring film; and blocking some of the rays by a pattern so that the ink on that part of the roll not receiving the rays remains transferable and there after transferring said liquid ink to said copy sheet.

3. A method of printing a transferable coating replica of a pattern on to a printing member comprising the steps of applying to the printing member a normally volatile liquid transferable coating containing a solid marking pigment which is non-volatile and non-tacky which becomes non-transferable when heated; said ink consisting of particles of a non-melting colloidal pigment such as graphite, suspended in a volatile solvent; radiating heat producing rays through a pattern against the printing member thereby driving off the volatile liquid part of said transferable ink to leave a non-tacky, non-transferring film; and blocking some of the rays by the patern so that a replica of said transferable coating remains on the printing.

member and thereafter transferring said liquid coating to said printing member.

4. The method of providing from an original having a pattern thereon a transferable replica of the pattern comprising the steps of applying to a printing member a volatile liquid transferable ink containing a solid mark ing pigment which is non-volatile andnon-tacky which becomes non-transferable when heated; said ink consisting of particles of a non-melting colloidal pigment such as graphite, suspended in a volatile solvent; radiating heat rays from a source in a path to said printing member, ab-

sorbing some of the heat rays in said path in accordance with a pattern so that ink in areas of the printing member corresponding to the pattern of the absorbed heat rays remains transferable and thereafter transferring said liquid coating to each printing member.

5. The method of printing copies comprising applying to a roll a normally liquid transferable ink containing a solid marking pigment which is non-volatile and non tacky which becomes non-transferable when heated; said ink consisting of particles of a non-melting colloidal pigment, such as graphite, suspended in a volatile solvent; radiating heat-producing rays to the roll thereby driving off the volatile liquid part of said transferable ink to leave a non-tacky, non-transferring film; blocking some of the rays by the pattern to be copied so that the ink not receiving the rays provides transferable replica while the ink receiving the rays becomes dried by heating so that it is non-transferable; and passing 'copy material in' contact with the roll so that the liquid ink image is transferred imagewise and indiciawise thereto. 9

References Cited in the file of this patent UNITED STATES PATENTS 1,618,505 Beebe et a1 Feb. 22, 1927 2,503,758 Murray Apr. 11, 1950 2,503,759 Murray Apr. 11, 1950 2,616,961 Groak Nov. 4, 1952 2,629,671 Murray Feb. 24, 1953 2,756,143 Murray July 24, 1956 

1. A METHOD OF PRINTING FROM AN ORIGINAL PATTERN TO A COPYSHEET A TRANSFERABLE REPLICA OF LIQUID INK COMPRISING THE STEPS OF APPLYING TO A PRINTING MEMBER A VOLATILE LIQUID TRANSFERABLE INK CONTAINING A SOLID MARKING PIGMENT WHICH IS NON-VOLATILE AND NON-TACKY WHICH DRIES TO FORM A CONTINUOUS NON-TACKY FILM AND BECOMES NON-TRANSFERABLE WHEN DRIED BY HEAT; SAID INK CONSISTING OF PARTICLES OF A NON-MELTING COLLOIDAL PIGMENT, SUCH AS GRAPHITE, SUSPENDED IN A VOLATILE SOLVENT; RADIATING HEAT-PRODUCING RAYS TO SAID PRINTING MEMBER THEREBY DRIVING OFF THE VOLATILE LIQUID PART OF SAID TRANSFERABLE INK TO LEAVE A NONTACKY, NON-TRANSFERRING FILM; AND BLOCKING SOME OF THE RAYS BY A PATTERN SO THAT THE INK IN AREAS OF THE PRINTING MEMBER CORRESPONDING TO THE BLOCKED RAYS REMAINS TRANSFERABLE AND THEREAFTER TRANSFERRING SAID LIQUID INK TO SAID COPY SHEET. 